1. Field of the Invention:
This invention relates to an electrode positioning mechanism of an electric arc or reduction furnace, in particular for smelting steel. The positioning mechanism includes a guide column having a mast arm to hold the electrode. The guide column is guided in a guide frame and can be moved vertically, by front and lateral guide rollers located in a nest, wherein there are mechanical damping elements to damp mechanical vibrations.
2. Description of the Prior Art: U.S. Pat. No. 4,422,172, incorporated herein by reference, discloses rollers located in a sleeve or nest, which makes possible the vertical movement of an electrode mast arm on a guide column. The guide column and mast arm, however, are vibrationally coupled to one another.
German Laid Open Patent Application No. DE-OS 28 37 741 incorporated herein by reference, discloses an electrode mast arm with a damping element to damp mechanical vibrations. The damping element is located between the mast arm and the electrode or between the mast arm and a point located outside the electrode positioning mechanism. In this prior art apparatus, there is a vibrationally solid coupling between the guide column and the guide frame.
This aforesaid coupling between the column and the frame has the disadvantage that the mass of the guide frame is included in the vibration system, of which the electrode is also a part. A further disadvantage of the coupling is that the individual components of the electrode positioning mechanism can excite one another to vibrations. To damp the system, therefore, high damping forces are required. For this purpose, dampers with large masses and large dimensions are necessary, which make the mast arm structure significantly heavier and larger. In turn, a more powerful drive system is required to raise and lower the mast arm structure.
The same German laid open patent above, discloses hydraulic elements to damp mechanical vibrations, wherein the damping effect is produced in throttles located in hydraulic cylinders. The use of these hydraulic dampers has the disadvantage that the damping action, on one hand, is not particularly effective and, on the other hand, because of the high thermal stresses exerted by the furnace environment, the assembly is subjected to severe fluctuations in its effectiveness. A further disadvantage is that the hydraulic system does not have any return force. Accordingly, the hydraulic elements can be moved by the guide column in one direction only, and the guide column overall is not centered in the guide frame.
One aspect of the invention resides broadly in a electrode positioning apparatus for an electric arc furnace wherein the electrode is supported by a mast arm and guide column and the guide column is supported for vertical movement by guide roll apparatus mounted on a guide frame, the electrode positioning apparatus includes a vibration damping device interposed between the guide roll means and the guide frame.
Another aspect of the invention resides broadly in a vibration damping apparatus for the electrode positioning mechanism of an electric arc furnace, wherein the electrode is supported by mast arm and guide column and the guide column is supported for vertical movement by guide roll means mounted on a guide frame, the vibration damping apparatus includes a vibration damping device interposed between said guide roll apparatus and said guide frame.